Transmission problem...what C6 interchanges?

[Evan's f250]

I have a 1978 F250 4x4 with a 400, 203 full time t-case, and a C-6 trans. I'm in need of a C6 trans & I'd like a lil more knownledge on what would be interchangable with mine. I believe I need a 351M/400, 460 bolt pattern 4x4 C6 trans to swap into mine, but does it matter what transfer case was originally attached to the trans?....In other words, if I was to find a C6 out of a 1977 F150 with a 351m, 205 t-case, could I bolt my 203 t-case to it and be ready to go??? Also, I know some of the 80-82 trucks had the 351m/400 too, would a C6 from one of those work as well??

Thanks in Advance,
Evan

 

[Mil1ion]

You need a C6 from a 78/79 4x4 or newer in the 80's with a 351M/400 Engine
The T/C is different from 351M/400 vs the 460 so you need that to be correct to the engine

Nothing from 77 and earlier will work because of the NSS position on the Trans shifter

 

[Evan's f250]

Appreciate the info. So, it doesn't matter which transfer case was originally bolted to it? If it had a 205, my 203 would bolt right up? Thanks again.

 

[Evan's f250]

I found a couple 78-79 broncos being parted out, I figure the C6 in those would be the same as a regular pickup? I appreciate the knowledge, I wasn't aware that one from a 77 wouldn't work..I'm glad I asked. I mainly wasn't sure if it mattered what t-case was original bolted to it?

 

[DNFXDLI]

As far as I know they should be...I don't know for sure....Doug has posted the 78 manual that should have the views of both...I'm not sure if the two transfer cases would have the same patterns...there is an intermediate housing that goes from the transmission to the transfer case....it might be the same or different...big help huh?

 

[Evan's f250]

Ok. I'm hoping they're the same. Would just like to know for sure before I buy one. I'm sure Mil1ion or someone will chime in with the answer to that.

 

[primetime]

The t-cases all share the same bolt pattern and spline count. Be aware, there are short shaft and long shaft 4x4 trannies. I`ve seen Broncos with long ones, and trucks with short ones. All the long ones I`ve seen had a cast iron adapter between the trans and t-case, while short ones are aluminum.

 

[Fellro]

As far as trans case goes, there will be no changes as long as what it attaches to is 351M/400 or 429/460. The mounting flange for the t-case is the same no matter, the difference is in the adapter, not the trans case. Hadn't heard the differing tailshafts on 4x4, but can't say I am surprised. You could possibly find a 77.5 or so with the 351M/400, but that is pretty much as far as you go. the key is the bell housing, year isn't a factor so much. Typical production says no older. Now, if there was a frame swap or such, anything goes.

 

[BuzzGun79]

Evan the outputshaft on my C-6 is 18 1/2 " although my invoice does not give a manufactor.the part number is ...036678D my truck was originally a 351M C-6 The stock Transfer case remains,i believe its the 205.....my trans was originally 2wd rebuilt to accomodate 4wd

 

[Evan's f250]

Thanks guys I appreciate it.

 

[Evan's f250]

I'm pretty sure my trans is out, here is what's going on:

I took the truck out for a drive the other day, I got about 1/2 mile and I heard two slight clunks from either the trans or t-case, directly after this noise, the rear end locked up for a second. The trans would then only pull in 1st gear, I could get it to stay in 2nd for a bit and then it would just start slipping, causing me to have to limp home in 1st. The transmission thew out about 2 qts of fluid on the way home (about a 1/2 - 3/4 mile) Trans fluid was everywhere, the headers even caught on fire from the burning fluid!

The ATF fluid smells burnt on the dipstick & I loosened up the plug on the transmission pan (aftermarket pan) & it looks to have some black coloration & that bad burnt smell.

The crazy thing is, the truck will drive fine in the yard, but once I drive it out on the road it does the same as above after it goes threw the gears.

I've drained the differentials & they both look clean, no shavings. No excessive slop in the u-joints or at the rear of the diffs.

I've also drained the t-case, the fluid was clean, no shavings. no weird fluid smells, the chain had some slop with the t-case in neutral, but that may be normal.

I will drop the trans pan this week, I've just never heard of a trans going out & causing the rear end to lock up for a bit. From the smell of the ATF fluid & checking everything else, I'm leaning towards a bad trans.